A known current sensor which includes a magnetic detection element, for example, a Hall element, has been used for measuring the electric current in a conductor. According to such current sensors, a positional relationship between a flux concentrating core that concentrates magnetic fluxes and the magnetic detection element that detects the magnetic flux density of the flux concentrating core significantly influences on a downsizing of a current sensor and a precision of an electric current detection. Thus, positioning the flux concentrating core and the magnetic detection element with high precision is desired. Further, in a case where a lead (wire) serves as a terminal of the magnetic detection element, it is desired to appropriately connect the lead (wire) to, for example, a land of a circuit board because a joining state of the lead (wire) and the circuit board significantly influences on a reliability (quality attributes) of the current sensor. For example, JP2002-243767A (hereinafter referred to as Patent reference 1) and JP2012-181208A (hereinafter referred to as Patent reference 2) disclose the types of known current sensors or devices explained above.
According to the electric current detection device disclosed in Patent reference 1, a core having a substantially rectangular shape in cross-section which is provided with a gap at one of four sides is fixed in a case. A Hall IC positioned in the gap detects changes in the magnetic flux generated at the core. A lead (wire) of the Hall IC is formed in a predetermined configuration, and is directly connected to connector terminals for input and output that are integrally formed with the case.
According to the current sensor disclosed in Patent reference 2, a substantially ring shaped core having a gap with a predetermined distance is integrally formed with a resin-made case, at least a portion of the gap is exposed to an accommodation portion of the resin-made case, and a magneto-electric converting element mounted on a circuit board housed in the accommodation portion is positioned at the gap. A lead type magneto-electric converting element in which a lead (wire) protrudes from a mold portion is applied as the magneto-electric converting element. The mold portion includes a tapered portion which is formed to be thinner in a distance direction of the gap as being away from the circuit board in a thickness direction of the circuit board. At least a portion of tapered outer surface of the tapered portion faces end surfaces of the core in the distance direction of the gap.
The electric current detection device disclosed in Patent reference 1 does not define the positional relationship between the core and the Hall IC. Thus, by a variation, or unevenness of a bend dimension when forming the lead of the Hall IC, the positional relationship between the core and the Hall IC greatly fluctuates and significantly influences on a precision in current detection. Further, because the Hall IC is not fixed relative to the core, when the Hall IC moves, for example, by vibrations, the precision in detection may be affected and there is a possibility that the electric current cannot be measured with high precision, or accuracy. As an alternative structure, a fixing member may be applied to fix the Hall IC relative to the core, however, this construction increases manufacturing costs.
According to the electric current sensor disclosed in Patent reference 2, when soldering the lead (wire) to the circuit board, the lead has to be directly inserted through a through hole of the circuit board, and a stress is generated at the lead if the lead is inserted through the through hole and soldered in a state where the position of the lead and the position of the through hole is offset, or not aligned. When the vibration and/or thermal shock (flame impingement) occurs in the foregoing state, portions soldered in accordance with a difference in linear coefficient of expansion of each of the magneto-electric converting element, the circuit board, and the resin-made case may be fatigued by repetitive stresses to causes problems in durability.
A need thus exists for a current sensor which is not susceptible to the drawback mentioned above.